Backing plate for strainers



April 15, 1952 FIG. 2

A. D. RUTHERFORD, JR

BACKING PLATE FOR STRAINERS Filed May 21, 1949 lNl/ENTOR A. D. RU THERFORD JR! ATTORNEY Patented Apr. 15, 1952 BACKING PLATE FOR STRAINER'S Albert 1). Rutherford, Jr., Essex, Md., assignor to Western Electric Company, Incorporated, New York, N. Y, a corporation of New York Application May 21, 1949, SerialNo. 94,688

4 Claims. 1

This invention relates to backing plates for strainers, and more particularly to backing plates for strainers used in straining elas'tomer compounds as they are extruded into finished-article form.

In the manufacture of insulated conductors, elastomer compounds often are extruded into coverings around conductive cores. and are some times strained as they are so extruded. .|Strainers known hitherto have caused caking of; the compounds being strained therethrough, have been diiilcult to clean, have broken easily and have seriously impeded flow of compound therepast.

An object of the invention is to provide new and improved backing plates for strainers.

A further object of the invention is to provide new and improved backing plates for strainers used in straining elastomer compounds as they are extruded into finished-article form.

An apparatus illustrating certain features of the invention may include a backing plate for an extruder, which comprises a plurality of radially spaced, concentric rings, at least one of the rings having a plurality of spacers projecting therefrom and so constructed and arranged that they detachably interlock with an immediately adjacent ring.

A complete understanding of the invention may be obtained from the following detailed description of a backing plate forming a; specific embodiment thereof, when read in conjunction with the appended drawing, in which:

Fig. 1 is a fragmentary, horizontal section of an apparatus including a backing plate forming one embodiment of the invention, and

Fig. .2 is an enlarged vertical section taken along line 2-2 of Fig. l.

Referring now in detail to the drawing, a stock screw I forces a highly accelerated compound l2 including rubber, or a synthetic, rubber-like elastomer, as its essential ingredient along a bore I3 formed in an extruding cylinder M. The compound I2 is forced through a strainer l6 positioned in a socket l8 formed in an extruding head 20 concentric with a tapered passage 22 in a toolholder 24 aligned with the stock screw Ill.

The tool-holder 24 is mounted removably in the head 20 by a nut 28 and bushings 30 and 32.

An aligning plate 34 holds a core guide 36 and extruding head 20, and includes a fine mesh straining screen 46, a coarse mesh backing screen. 48 and a segmental backing plate 50. The backing plate 50 includes a central section 52, an intermediate section 54 and an outer section 56. The section 52 includes a frustoconical ring 58 having radial arms Bil-Bil, which fit into a frustoconical socket 62 in a frustocom'cal ring 154 of the intermediate section 54. Arms 65-56 of the section 54 project radially outwardly from the ring 64, and'fit into a frustoconical socket, 61- in a frustoconical ring 58 of the outer section, 56. Arms 10-10 project radially outwardly from the ring 68 and rest in a tapered socket 12 in a retaining ring 14 which fits into the socket I8 in the extruding head 20. I

The arms -60, 66-56 and Ill-1D are formed by cutting slots 15-15,, 11-11 and 19-19 in; blanks having the general outlines of the sections. The slots 15-15,, 11-11 and 19- 9 are cut by moving milling cutters along the sections in directions from one face of each section to the other faces of each section parallel to the frustrum surface thereof. Hence, the cross-sectional area, of each slot is constant from one face of the section to the other thereof, and the arms taper from greater widths on the supporting faces, thereof to lesser Widths directly therebehind. Thus, the slots do not constrict the flow of the compound, and the tapered arms permit compound to be removed from the slots easily in cleaning the sections.

Operation The compound I2 is forced continuously along the extruding cylinder l4 by the stock screw I0, and flows along the tapered passage 22. The compound passes through the strainer l6 freely because the slots 15-15, 11-11 and 19-19 permit this flow. The radial, generally wedgeshaped, slots 15-15, 11-11 and 19-19 provide flow-passages of large cross-sectional area so that the compound flows through the backing plate 50 with a minimum obstruction, and the sections provide excellent support for the backins screen.

The strainer may be removed with case from the socket I8 in the extruding head. The sections 52, 54 and 56 may easily be disassembled by moving the section 52, relative to the section 0 54, toward the left, as viewed in Fig. 1, then moving the section 54 in the same direction relative to the section 56, and then moving the section 56 in the same direction with respect to the retaining ring 14,, The backing plate is simple The strainer l5 nests in the socket I8 in the 66 to clean since the slots 15-15, 11-11 and 19-19 are wedge-shaped in two directions, and have open ends through which the compound may be pulled.

What is claimed is:

l. A segmental backing plate for a straining screen in an extruder, which comprises an outer segment including a ring having a plurality of spaced radial arms on the outer periphery thereof and having the inner periphery thereof tapered longitudinally of the ring so as to constitute a frustoconical socket, an intermediate segment including a second ring having a plurality of spaced radial arms on the outer periphery thereof and having the inner periphery thereof tapered longitudinally of the second ring so as to constitute a frustoconical socket, said intermediate segment having such an outside configuration that it may be removably seated within the frustoconical socket in the outer segment, and a central segment including a third ring having a plurality of spaced radial arms on the outer periphery thereof and having such an outside configuration that it may be removably seated within the frustoconical socket in the intermediate segment.

2. A segmental backing plate for a straining screen in an extruder, which comprises an outer segment including a frustoconical ring having a plurality of spaced radial armson the outer periphery thereof, and an inner segment including a ring having a plurality of spaced radial arms on the outer periphery thereof and having such an outside configuration that it may be removably seated within the frustoconical ring of the outer segment.

3. A segmental backing plate for a. straining screen in an extruder, which comprises an outer segment including an annular plate having a plurality of passageways extending longitudinally through the annular plate, said passageways being of constant cross-sectional area throughout their lengths, the inner periphery of the annular plate being tapered from one side to the other side thereof so as to constitute a frustoconical socket, and an inner segment including a plate having a plurality of passageways of constant cross-sectional area extending longitudinally 4 through the plate, the outer periphery of the inner segment having a taper corresponding to the taper of the fr-ustoconical socket in the outer segment so that the inner segment may be removably seated within the socket in the outer segment.

4. A segmental backing plate for a straining screen in an extruder, which comprises an outer segment including a frustoconical ring having a plurality of spaced radial arms on the outer periphery thereof, an intermediate segment including a second fr-ustoconical ring having a plurality of spaced radial arms on the outerperiphery thereof and having an outside taper corresponding to the inner taper of the first frustoconical ring so that the intermediate segment may be removably seated within the frustoeonical ring of the outer segment, and a central segment including a third frustoconical ring having a plurality of spaced radial arms on the outer periphery thereof and having an outside taper corresponding to the inner taper of the second.

frustoconical ring so that the central segment may be removably seated within the frustoconi-' cal ring of the intermediate segment, the radial arms of each of said segments being so tapered from one side of each segment to the other side thereof that when the segments are assembled one Within the other to form the backing plate the spaced radial arms will form converging passage-a ways having constant cross-sectional areas through the backing plate.

ALBERT D. RUTHERFORD, 'JRI I REFERENCES CITED 7 The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Apr. 28, 1927', 

